Union Beach was formed as a borough by an Act of the New Jersey Legislature on March 16, 1925, from portions of Raritan Township (now Hazlet), based on the results of a referendum held on April 16, 1925.
Union Beach is part of the Bayshore Regional Strategic Plan, an effort by nine municipalities in northern Monmouth County to reinvigorate the area's economy by emphasizing the traditional downtowns, dense residential neighborhoods, maritime history, and the natural beauty of the Raritan Bayshore coastline.
As of the census of 2000, there were 6,649 people, 2,143 households, and 1,722 families residing in the borough. The population density was 3,545.1 people per square mile (1,365.5/km²). There were 2,229 housing units at an average density of 1,188.5/sq mi (457.8/km²). The racial makeup of the borough was 94.45% White, 0.87% African American, 0.20% Native American, 1.23% Asian, 1.35% from other races, and 1.90% from two or more races. Hispanic or Latino of any race were 8.09% of the population.
There were 2,143 households out of which 43.3% had children under the age of 18 living with them, 62.7% were married couples living together, 12.2% had a female householder with no husband present, and 19.6% were non-families. 15.5% of all households were made up of individuals and 5.5% had someone living alone who was 65 years of age or older. The average household size was 3.09 and the average family size was 3.44.
In the borough the population was spread out with 29.1% under the age of 18, 8.3% from 18 to 24, 33.0% from 25 to 44, 22.1% from 45 to 64, and 7.5% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 102.0 males. For every 100 females age 18 and over, there were 97.9 males.
The median income for a household in the borough was $59,946, and the median income for a family was $65,179. Males had a median income of $45,688 versus $29,918 for females. The per capita income for the borough was $20,973. About 4.2% of families and 4.8% of the population were below the poverty line, including 5.6% of those under age 18 and 5.9% of those age 65 or over.